127 
180° C. for four hours and the soil leached with distilled water. 
To our great surprise these water extracts of heated soil were 
brown in color and had an odor of caramel. They proved to be 
such favorable media for Pyronema and other fungi that we were 
unable to preserve the solutions except by sealing the bottles 
at the temperature of boiling water. On the other hand, the 
extracts of unheated soil were colorless, practically odorless, and 
were never infected with fungi of any sort. 
With these dark-colored extracts at our command, we made a 
great variety of tests. We found that these extracts were ideal 
culture media for Pyronema, Fusarium, Penicillium, etc., and that 
the addition of large quantities of such extracts to heated soils 
caused them to become more favorable to Pyronema growth than 
capable of supporting the growth of the fungi. It should be 
resulted in complete failure. The reason for this is not clear, 
but it may well be that the adsorptive and decolorizing effects of 
the finely divided soil are similar to those of bone-black. Some 
of the dark-colored extracts were distilled in the hope of sepa- 
rating the volatile and non-volatile substances into fractions with 
different properties. This attempt likewise failed, for Pyronema 
grew both in the colorless distillate and in the dark distillation 
residue, the growth being most abundant in the latter, since it 
was more concentrated. We heated some soil in a combustion- 
tube and caught the products of the dry distillation in water; 
the solution thus obtained was alkaline to litmus and had the 
very offensive odor of pyridine bases. The solution seemed 
neither to inhibit nor to stimulate the growth of Pyronema. 
From this experiment and others, it does not seem likely that the 
beneficial effects of heating the soil are due to the driving off of 
unfavorable substances, but to certain changes produced in the 
soil itself. The extracts of heated soil were acid to litmus, gave 
many tests for organic acids, responded to the tests for carbo- 
hydrates, and finally, showed a strong reducing action upon 
